Refractory siliceous cements and their method of production

ABSTRACT

This invention relates to refractory siliceous barium cements characterised in that their clinkers have a chemical composition expressed in oxides of : 75 to 82 % BaO, 14 to 17 % SiO2, less than 3.5 % Al2O3, less than 1.5 % Fe2O3, less than 2 % CaO, less than 1 % MgO, less than 1 % Na2O + K2O, for a total of 100 %, all percentages being by weight, and the utilisation of these cements for producing refractory concretes.

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United States Patent [191 Walter [451 July 29,1975

1 1 REFRACTORY SILICEOUS CEMENTS AND THEIR METHOD OF PRODUCTION [76] Inventor: Liviu Walter, l1 Impasse Houssay,

Related US. Application Data [63] Continuation of Ser. No. 165,404, July 22. 1971,

abandoned.

[30] Foreign Application Priority Data Aug. 4, 1970 France 70.28783 [52] US. Cl. 106/85; 106/89; 106/100;

[51] Int. Cl C04b I/00 [58] Field of Search 106/85, 89, 100, 104

[56] References Cited OTHER PUBLICATIONS Lea & Desch, The Chemistry of Cement and Concrete, Ed. Arnold (Pub.) Ltd., London, 1956, p. 472.

Primary Examiner-J. Poer [57] ABSTRACT This invention relates to refractory siliceo s b cements characterised in that their m% c emical composition expressed in oxides of 75 to 82 BaO, 14 to 17 SiO less than 3.5 A1 0 less than 1.5 Fe O less than 2 CaO, less than I MgO, less than 1 Na O K 0, for a total of 100 all percentages being by weight, and the utilisation of these cements for producing refractory concretes.

5 Claims, No Drawings REFRACTORY SILICEOUS CEMENTS AND THEIR METHOD OF PRODUCTION This is a continuation of application Ser. No. 165,404 filed July 22, l97l now abandoned.

This invention concerns new refractory siliceous cements and their method of production. For the preparation of refractory concretes, i.e., concretes resi ting temperatures above l,500C, refractory cements are used. These cements are aluminous cements, very poor in fluxes, based on calcium dialuminate and calcium monoaluminate.

Such cements have a very high refractoriness (from l,600 to l.750 C for instance), but they present two main disadvantages:

a. they have a high cost price,

b. they have a relatively poor behaviour concerning their softening under load at high temperature when they are used with refractory granulates made from crushed aluminosilicate fire-bricks containing less than 40 A1 with sillimanite or mullite granulates and especially when they are used with very porous siliceous granulates for insulating concretes.

At present, refractory siliceous barium cements based on dibarium silicate are unknown.

This invention concerns, as new products, refractory siliceous barium cements. The refractory siliceous barium cements based on dibarium silicate are manufactured according to this invention, by baking to vitrification or fusion 1 ,500 to l,700C) a homogeneous mixture of very fine powders of raw materials containing mainly barium, silicon and oxygen, and are characterised in that their clinkers have a chemical composition, expressed in oxides, of 75 to 82 BaO, 14 to l7 SiO less than 3,5 AI O less than 1,5 Fe O less than 2 CaO, less than I MgO, less than 1 Na O K 0, for a total of 100 all percentages being by weight.

The cement clinkers, according to the invention, have a mineralogical constitution, expressed in hydraulic constituents of 70 to 90 dibarium silicate, ZBaO SiO as hydraulic main-constituent and of:

less than 8 monobarium silicate; BaO SiO less than 8 monobarium aluminate, BaO A1 0 less than 8 tetrabarium aluminateferrite, 4BaO Al O .Fe O

less than 12 calcium-barium orthosilicate, CaO

BaO SiO together with magnesium-barium orthosilicate, MgO BaO SiO as hydraulic secondaray constituents.

To the cement clinker, according to the invention, there is added, during the very fine grinding, an additional compound intended to slow down the setting of this cement. It was ascertained in fact that the setting of this cement is otherwise too rapid and that it is of interest, as is the case, for instance, with the portland cement, to add a setting-retarder. Calcium sulfate or gypsum in quantities of about 3 to or 3 to 5 gypsum together with 5 bentonite are used to this end.

It is also possible to add other additives known per se.

This invention also concerns the methods of producing cement-clinkers and cements according to the invention. These methods are characterised in that the raw materials containing mainly barium silicon and oxygen, are very finely ground to powders, then admixed and homogenised, the relative quantities of the powthe invention, to the formation of S0 and S0 These oxides are obviously recuperated to be put to value according to known methods. 7

If the refractory siliceous barium cements are produced simultaneously with sulphuroxides for the manufacture of sulfuric acid and its derivatives, the use of barytes becomes economical because its desulfatation in the raw material mixtures is greatly facilitated, occurring at lower temperatures (reactions in solid state), and because, under these conditions, the general production costs diminish substantially.

The refractory siliceous barium cements based on dibarium silicate, according to the invention, present the following advantages in comparison with the refractory aluminous cements based on calcium monoaluminate and calcium dialuminate:

they are cheaper, the barytes having a lower cost price than the artificial alumina or the very pure natural hydrated alumina;

they have higher mecanical strengths 24 hours after mixing with water:

their hydration takes place with lower water quantities, thus leading to lower porosities after hardening and smaller contractions after calcination:

they do not expand during setting and consequently can be rapidly removed from the shuttering.

As hydraulic binders for refractory mortars and concretes with refractory granulates made from crushed alumino-silicate bricks containing less than 40 M 0 with sillimanite or mullite granulates and for insulating concretes with very porous siliceous granulates of expanded fireclays for instance, they can be used at higher temperatures of 100 to 150 "C because of their superior resistance to softening under load at high tern;

perature.

Ground and homogenised with 20 to by weight, of basic or acid high furnace slag, poor in A1 0 they can be used as unequalled sulfate-resisting cements or sea water cements.

Ground and homogenised with 30 to 60 barytes, they can be used as shieiding cements of great value, absorbing X- and gamma-radiations.

The following non limiting example illustates this invention without however limiting its scope.

EXAMPLE 91 parts by weight of siliceous barytes and 9 parts by weight of siliceous clay are very finely ground, then admixed and homogenised. The raw materials used have the following chemical composition: Siliceous barytes: 4.52 SiO 0.78 A1 0 0.42 Fe O 0.56 CaO, 61.08 BaO, 0.35 MgO, 0.26 alkalis, 31.84 0.41 CO Siliceous clay: 73.95 SiO 12.58 A1 0 5.8l Fe o 0.92 CaO, 0.47 MgO, 0.90 alkalis, 5.66 loss on ignition.

The above mixture is baked until clinkers are formed (at 1,500 to 1,600C) in a usual cement furnace. After cooling, the resulting cement clinker is ground as finely as artificial Portland cement together with 4.5 of gypsum as setting retarder.

The raw material mixture contains 23 which emanates during formation of clinkers and is recuperated to be then used according to known methods.

The refractory siliceous cement clinker resulting from the above method of production has the following chemical composition:

15.30 SiO,, 2.62 A1 0 1.29 Fe O 0.84 CaO, 78.99 BaO, 0.51 MgO. 0.45 alkalis.

lts mineralogical constitution is: 77.10 dibarium silicate, 2BaO SiO as main constituent and 3.63 monobarium silicate, BaO SiO 4.51 monobarium aluminate, BaO A1 0 7.06 tetrabarium aluminateferrite, 4 BaO A1 0 Fe O 4.04 calcium-barium orthosilicate, CaO BaO SiO 3.21 magnesiumbarium orthosilicate, MgO.BaO.SiO- as secondary constituents and 0.45 alkalis, free and included in the barium-belite (mineralised dibarium silicate).

Without gypsum, the setting of this cement is very rapid. With the very finely ground and homogenised addition it becomes normal. Its hardening is very rapid (high mechanical strengths 24 hours after mixing with water).

It has a refractoriness of 1,670C, and its compressive strengths, after 12 hours in humid air and then in water, are the following:

450 kg/cm after 24 hours,

600 kg/cm after 3 days,

660 kg/cm after 7 days, and

730 kg/cm after 28 days.

The refractory concrete prepared from 15 of cement and 85 of refractory granulates made from crushed aluminosilicate brick containing 30.2 A1 0 having 16 of the total weight of the concrete granules of less than 0.2 mm, 32 granules between 0.2 and 2 mm and 32 granules between 2 and 5 mm, has a refractoriness of 1,630C. The refractoriness under load of 2 kg/cm of the refractory concretes realised with this refractory siliceous barium cement together with refractory granulates made from crushed aluminosilicate fireclay bricks containing 30.2 A1 0 having the above granulation, is 1,330C, 120C higher than the refractoriness under load of the corresponding refractory concretes realized with the refractory aluminous cements based on calcium monoaluminate and calcium dialuminate, which is only of 1,210C. This results in consequence in a much greater field of use for these less refractory concretes and in a lower cost price.

I claim:

1. A refractory siliceous barium cement containing as the major constituent dibarium silicate and comprising as minor constituents monobarium silicate, monobarium aluminate. tetrabarium aluminate ferrite, calcium-barium orthosilicate and magnesium-barium orthosilicate, said constituents being present in such proportions that the cement in its clinker stage contains by weight from to 82% BaO. from 14 to 17% $0,, less than 3.5% A1 0 less than 1.5% Fe o less than 2% CaO, less than 1% MgO and less than 1% alkalis.

2. Method of producing refractory siliceous barium cement clinkers containing as the major constituent dibarium silicate and comprising as minor constituents monobarum silicate, monobarium aluminate, tetrabarium aluminate ferrite, calcium-barium orthosilicate and magnesium-barium orthosilicate in such proportions as to provide from 75 to 82% BaO, from 14 to 17% SiO less than 3.5% A1 0 less than 1.5% Fe O less than 2% CaO, less than 1% MgO and less than 1% alkalis which comprises baking to vitrification a homogeneous mixture of very fine powders containing a source of barium, silicon, and oxygen in sufficient quantity and relative proportions to permit the formation upon vitrification of 70 to by weight, of dibarium silicate.

3. A refractory siliceous barium cement which contains from 70 to 90% by weight of dibarium silicate and from 10 to 30% by weight of monobarium silicate, monobarium aluminate. tetrabarium ferrite aluminate, calcium-barium orthosilicate and barium-magnesium orthosilicate, with the proviso that the composition does not contain more than 8% monobarium silicate. nor more than 8% monobarium aluminate, nor more than 8% tetrabarium aluminate ferrite and not more than 12% of calcium-barium orthosilicate and magnesium-barium orthosilicate; in combination with a settingretarder.

4. The composition of claim 3, wherein the setting retarder is 3 to 5% of calcium sulfate or gypsum.

5. The composition of claim 3, wherein the setting retarder is 3 to 5% of gypsum together with 5% bentonrte. 

1. A REFRACTORY SILICEOUS BARUIM CEMENT CONTAINING AS THE MAJOR CONSTITUENT DIBARIUM SILICATE AND COMPRISING AS MINOR CONSTITUENTS MONOBARIUM SILICATE, MONOBARIUM ALUMINATE, TETRABARIUM ALUMINATE FERRITE, CALCIUM-BARIUM ORTHOSILICATE AND MAGNESIUM-BARIUM ORTHOSILICATE, SAID CONSTITUENTS BEING PRESENT IN SUCH PROPORTIONS THAT THE CEMENT IN ITS CLINKER STAGE CONTAINS BY WEIGHT FROM 75 TO 82% BAO, FROM 14 TO 17% SIO2, LESS THAN 3.5% AL2O3, LESS THAN 1.5% FE2O3, LESS THAN 22% CAO, LESS THAN 1% MGO AND LESS THAN 1% ALKALIS.
 2. Method of producing refractory siliceous barium cement clinkers containing as the major constituent dibarium silicate and comprising as minor constituents monobarum silicate, monobarium aluminate, tetrabarium aluminate ferrite, calcium-barium orthosilicate and magnesium-barium orthosilicate in such proportions as to provide from 75 to 82% BaO, from 14 to 17% SiO2, less than 3.5% Al2O3, less than 1.5% Fe2O3, less than 2% CaO, less than 1% MgO and less than 1% alkalis which comprises baking to vitrification a homogeneous mixture of very fine powders containing a source of barium, silicon, and oxygen in sufficient quantity and relative proportions to permit the formation upon vitrification of 70 to 90%, by weight, of dibarium silicate.
 3. A refractory siliceous barium cement which contains from 70 to 90% by weight of dibarium silicate and from 10 to 30% by weight of monobarium silicate, monobarium aluminate, tetrabarium ferrite aluminate, calcium-barium orthosilicate and barium-magnesium orthosilicate, with the proviso that the composition does not contain more than 8% monobarium silicate, nor more than 8% monobarium aluminate, nor more than 8% tetrabarium aluminate ferrite and not more than 12% of calcium-barium orthosilicate and magnesium-barium orthosilicate; in combination with a setting-retarder.
 4. The composition of claim 3, wherein the setting retarder is 3 to 5% of calcium sulfate or gypsum.
 5. The composition of claim 3, wherein the setting retarder is 3 to 5% of gypsum together with 5% bentonite. 